PROJECT SUMMARY Hepatitis C virus infection (HCV) is the most important cause of chronic infectious disease death in the US, with over 2 million people infected and nearly 20,000 dying annually. The greatest burden; occurs among ?baby boomers,? born 1945-1965 (75% of those infected). HCV disproportionately affects racial/ethnic minorities (25% of those infected are Blacks; Black mortality is 87% and Hispanic mortality 43% higher than among Whites), persons with HIV disease and injection drug users. Direct-acting antiviral (DAA) therapy recently became available; it can cure >95% of people with HCV, but only half have been diagnosed and a much smaller proportion treated. CDC?s National Viral Hepatitis Action Plan (NVHAP) calls for identification and treatment of all those infected, but access for racial/ethnic minorities is problematic, due to costly medicines, stigmatization of those with HCV, variable access to specialists, inconsistent provider awareness of need to diagnose and treat, and variable coverage of treatment, particularly by state Medicaid plans. We propose to use an exploratory sequential mixed methods design to analyze HCV testing and treatment patterns among US baby boomers, tracking the diffusion of DAA therapy nationally and across demographic groups since initial licensing in 2014, and to conduct qualitative work and surveys of patients and physicians to explore factors contributing to disparities in care. The Specific Aims are: 1) To use national and state-level publicly-administered health insurance claims data to describe variations in HCV screening and treatment among the baby boomer cohort by a) examining differences in HCV screening rates across race/ethnicity, community socioeconomic status (cSES), and primary care utilization; b) evaluating the time between HCV diagnosis and antiviral treatment initiation among individuals with a new diagnosis of HCV, by race/ethnicity and cSES; and c) evaluating time between FDA approval of the first DAA HCV treatment, and initiation of DAA treatment for the prevalent population of baby boomers with chronic HCV, by race/ethnicity and cSES; and, informed by these findings 2) To assess the contribution of patient and provider factors to shaping disparities in diagnosis and treatment of HCV by adapting existing measures and/or developing novel measures, and administering these to samples of HCV patients and providers, by a) using patient focus groups and participatory feedback to adapt measures of stigma and discrimination in health care and other settings, knowledge and beliefs about HCV and its treatment, and barriers to care (competing needs, depression, drug use, access, patient costs, distance to care), then administering them to diverse HCV patients in two US regions; and b) developing measures of HCV knowledge, attitudes, experiences and practices among physicians, then administering them to primary care, gastroenterology, hepatology, and infectious disease physicians in two US regions. We will share study instruments and results with community partners, who will be very involved in all phases of the research, and with other key stakeholders and investigators, to facilitate the development and evaluation of interventions to address the problems identified in this study.